Coherence effect on decryption characteristics in message modulation type chaos secure communication systems using fiber-optic ring resonators

We numerically investigated the dependence of the decryption characteristics in a message modulation type chaos secure communication system using optical fiber ring resonators (OFRRs) on the coherence condition of carrier light. Since the output dynamics of OFRRs were formed on the basis of interference phenomenon among the circulated components in OFRRs, the coherence condition of input light affected inherently the OFRR output dynamics, resulting in the decryption characteristics. It was found that the decryption characteristics degraded as coherence length increased, i.e., as the spectral width of the input light decreased. The decryption characteristics also grew worse as the parameter differences between the transmitter and the receiver became larger.     

一种新型的双向长距离光纤混沌保密 通信系统性能研究

基于两个在驱动混沌信号注入下的响应半导体激光器之间的混沌同步, 提出了一种新型的可实现信息双向、长距离保密传输的系统, 并建立了相应的理论模型. 利用该理论模型, 研究了系统的双向传输性能、 安全性能以及系统性能随传输距离的变化. 结果表明: 两个响应激光器在受到发自同一驱动混沌激光器的混沌光注入下, 其混沌输出虽然与注入混沌信号相差很大, 但两个响应激光器的混沌输出却能实现非常好的无时间延迟的等时同步; 对窃听者可能获取信息的各个途径进行了考察, 结果显示该系统具有很好的安全性; 采用普通单模光纤作为传输信道, 信息经过50 km传输后, 解调信息Q因子可达到6以上; 采用色散位移光纤, 信息经过200 km的传输, 解调信息Q因子还可达6以上.     

光纤混沌双芯双向保密通信系统研究

把量子阱激光混沌耦合反馈同步系统应用于光纤保密通信中,提出光纤混沌双芯双向保密通信设想.通过耦合外部光注入多量子阱激光混沌全光耦合反馈同步系统和光纤传输信道,建立了光纤混沌双芯双向通信系统物理模型.理论和数值证明了激光混沌同步,理论分析指出光纤中的自相位调制是限制激光混沌在光纤传输中同步的主要原因,并推导出混沌信号双芯双向传输中的非线性相移以及混沌激光功率限制和传输距离公式.数值实现了该系统在长距离二根光纤传输中的同步,详细地分析了系统同步时间随光纤传输长度的关系.模拟了调制频率06 GHz的混沌模拟通 关键词： 混沌 同步 光纤 保密通信     

Bifurcation structures into chaos of delay-differential equations for a passive optical ring resonator

The delay-differential equation system describing the passive optical ring cavity is investigated. A survey of different bifurcation scenarios into chaos of the solutions on one branch and specific transitions between different branches of the multistable system are discussed. Precipitation via a heteroclinic cycle and crisis induced intermittency are found.     

The role of birefringence in modulation instability fiber ring resonators

We considered a high birefringence fiber ring cavity, which can be represented by a system of two incoherently coupled nonlinear Schrödinger equations with periodic boundary conditions. The stability of the system against time domain periodic perturbations could be strongly conditioned by fiber birefringence. We apply both a perturbative approach and a mean field approximation, in order to highlight the dependence of modulation instability on birefringence and ring detuning. We extend the study of the dynamical properties of the system by means of a phase matching interpretation and a selection of numerical solutions of the governing equations.     

光纤混沌相位编码保密通信系统理论研究

通过耦合激光混沌相位控制同步系统和光纤信道，提出外部光注入半导体激光器激光混沌相 位控制光纤同步以及混沌相位相移键控外调制光纤保密通信系统理论模型，数值实现了在相 位控制器控制下的远程光纤混沌同步.理论分析了光纤自相位调制对混沌信号以及对同步的 影响，导出了光纤混沌最大传输距离公式.通过连续键控调制相位控制器实现了光纤激光混 沌相位相移键控编码调制发射，设置接收系统相位控制器控制激光相位相移实现了光纤激光 混沌同步解调.数值模拟了具有比特率50Mbit/s远程光纤混沌数字编码通信系统的应用，详 细地进行了在远距离光纤传输中的系统参数失配以及系统抗噪声能力的数值分析. 关键词： 混沌 同步 光纤混沌通信 半导体激光器 相位     

The effects of pump phase modulation on noise characteristics of fiber optical parametric amplifiers

This paper investigates the effects of pump phase modulation (PM) on the noise characteristics of fiber optical parametric amplifiers (FOPAs) theoretically. The results show that the effect of the pump PM on the noise of FOPAs can be diminished by adjusting the structural parameters of amplifiers properly. The parameters of the pump phase modulation are optimized with several methods to reduce the noise of FOPAs.     

Two chaos synchronization schemes and public-channel message transmission in a mutually coupled semiconductor lasers system

Chaos synchronization and message transmission of a mutually coupled system consisting of two semiconductor lasers (SLs) and a partially transparent mirror (PTM) in between are investigated theoretically. Analytical results show that two types of chaos synchronization schemes, named as isochronal synchronization (IS) and leader/laggard synchronization (LLS), can be achieved by adjusting the reflectivity and position of PTM. By establishing SIMULINK model, numerical simulations illustrate that as the PTM is positioned at the center of two lasers, IS is available when the reflectivity of PTM is moderate. The LLS is achieved when the reflectivity of PTM equals to 0.5, which means feedback strength equals to coupling strength. Its lag time is just determined by the difference of feedback delay time. The investigations of mutual chaos pass filtering (MCPF) effects and the secure chaotic communication simulations indicate that IS allows real-time bidirectional message transmission on a public-channel, while LLS can achieve higher security chaotic communication by using its lag time as cryptography key. The demonstrated system can be used as a rudiment of array chaos communications system.     

基于半导体环形激光器的高速双向双信道混沌保密通信

提出了一种利用半导体环形激光器(SRLs)的新型高速双向、双信道混沌保密通信系统. 在该系统中, 首先利用交叉双光反馈对驱动激光器的顺时针模式和逆时针模式的混沌延时特征进行抑制. 然后将此混沌信号注入到一对响应激光器对应的顺时针模和逆时针模中, 以实现带宽的增强及混沌同步. 最后基于响应激光器之间的混沌同步, 实现高速率、双向、双信道的混沌保密通信. 通过对驱动激光器在交叉双光反馈作用下的混沌特性、以及响应激光器在不同条件下的同步特性进行了相关理论和仿真研究, 结果表明: 驱动激光器在合适的交叉双光反馈作用下可以产生延时特性被良好隐藏的顺时针模式和逆时针模式混沌信号; 在该混沌信号的注入下, 响应激光器输出的混沌信号带宽可以得到明显增强; 通过设置合适注入强度值和频率失谐值, 响应激光器之间可实现高质量的等时混沌同步. 最后, 对系统的双向、双信道混沌保密通信特性进行了讨论. 当10 Gbit/s信号传输距离为10 km时, 解调信息Q因子值仍可保持在6以上.     

Generation of bound solitons in actively phase modulation mode-locked fiber ring resonators

Bound solitons generated in actively mode-locked lasers enable new forms of pulse pairs and multiple pairs or groups of solitons in optical transmission or logics. In this paper, we present the generation of stable bound states of multiple solitons in an active mode-locked fiber laser using continuous phase modulation for wideband phase matching. Not only that dual-soliton bound states but also the triple- and quadruple-soliton pulses can be established. Simulation of the generated solitons are demonstrated. We have also prove by simulation that experimental relative phase difference and chirping caused by phase modulation of LiNbO₃ modulator in the fiber loop significantly influences the interaction between the solitons and hence their stability as they circulate in the anomalous path-averaged dispersion fiber loop.     

The spectral broadening of a blue optical pulse and the modulation of a pulse waveform in a photonic crystal fiber by induced-phase modulation

By copropagating a fundamental pulse and a blue second-harmonic pulse from a Ti:Sapphire oscillator in a photonic crystal fiber (PCF), the spectral broadening of the blue second-harmonic pulse from 380 to 600 nm has been observed by use of induced-phase modulation (IPM) at a 78-MHz repetition rate. From the experimental and the calculated delay time dependence of spectral intensities, it was inferred that the largest spectral broadening was observed when the second-harmonic pulse interacted with the fundamental pulse near the input end of a PCF, where the fundamental pulse was compressed temporally due to self-phase modulation and negative group velocity dispersion. From the simulation, the mechanism of spectral broadening was clarified and the fission process of the fundamental pulse was shown to be influenced strongly by IPM.     

Transient optical modulation properties in the terahertz metamaterial of split ring resonators

The ultrafast optical modulation properties of split ring resonators are characterized by utilizing optical pump-terahertz probe spectroscopy.The experimental results show that when the terahertz electric vector is perpendicular to the gap of the split ring resonator,resonant absorption can be quenched significantly under high pump excitation.However,when the terahertz electric vector is parallel to the gap,the resonant absorption is less sensitive to pump excitation due to the structural properties of the metamaterial.Our numerical simulations also demonstrate that the pump pulse significantly influences the split ring resonator current by generating carriers in the substrate.     

时空混沌系统在保密通信中的应用

以环形腔中激光振荡输出空间扩展模型为例，研究了多组信息同时编码的时空混沌加密及解密，给出安全可靠的加解密结果，并对抗破译能力进行了检验，完成了互联网上保密通信实验，结果令人满意。     

Self oscillations of a bistable element in two coupled hybrid ring resonators

A CdS crystal showing thermally induced optical bistability is incorporated into two coupled hybrid ring resonators with different delay times. Both delay times are much longer than the relaxation time of the nonlinearity. The resulting self-oscillations are investigated both experimentally and theoretically. We find two different types of oscillation modes. If the crystal is on the lower branch of the bistability during the longer delay time, step like oscillations similar to the case of a single resonator occur. If the crystal is in the lower state onlh for the shorter delay time (also the shorter of the two delay times is much longer than the relaxation time) we find more complicated modes with plateaus and stairs because the long resonator acts as a memory for the system state before the switching process. We find complex mode locking structures exhibiting Farey-tree like transitions between different oscillation modes as well as mode coexistence. Based on an adiabatic theory we compute the regions of extstence of the different oscillation modes and compare them with experimental results.     

带光纤环的分布式光纤拉曼温度系统

 为了抑制分布式光纤拉曼温度系统的温漂和瑞利散射光窜扰反斯托克斯散射光,在传感光纤前端盲区后放置光纤取样环,用瑞利散射光解调反斯托克斯散射光及用光纤取样环的温度计算光纤线上其它点的温度,提高了系统的测温精度和稳定性。采用功率100 mW,波长1.55 μm,脉宽10 ns脉冲激光器和15 dB前置光纤放大器,100M14bitA/D转换卡及DSP作数字平均构建光纤拉曼温度系统的实验,实现了测温误差在±0.03 ℃内。     

Carrier-induced optical bistability in silicon ring resonators

We demonstrate optical bistability in a micrometer-sized silicon ring resonator based on the free-carrier dispersion effect in silicon. We measure the transfer function of the resonator showing a hysteresis loop with an input optical power of less than 10 mW. The influence of the thermal optical effect, which is minimized in the experiment by use of nanosecond pulses, is evaluated theoretically. Applications include sequential logic operations for all-optical routing.     

Soliton control in optical lattices with periodic modulation of nonlinearity coefficient

We address the dynamics of solitons in the optical lattices with periodic modulation of the nonlinearity coefficient. Based on the quasi-particle approach, the properties of fundamental soliton localized in optical lattices are theoretically analyzed and shown its potential application for controllable soliton switching. Moreover, the phenomena of multi-soliton splitting and the single-soliton constituent trapping in the optical lattices are illustrated and discussed.     

An experimental investigation of the optical switching characteristics using an optical Sagnac interferometer incorporating one and two ring resonators

We present the use of a fiber optic Sagnac interferometer incorporating one and two fiber optic ring resonators to characterize experimentally the optical switching behaviors. These prototypes were formed by the Sagnac interferometer and serially connected to the ring resonators. The input optical signal was launched via one end of the interferometer, where the polarization control was employed to obtain the maximum optical transmission power. Results obtained have shown that the increasing in switching time (i.e. narrower spectral width) and power can be achieved.     

Pilot-added carrier-phase recovery scheme for Nyquist M-ary quadrature amplitude modulation optical fiber communication system

A new two-stage carrier-phase recovery scheme using a combination of an optical pilot-aided algorithm with the crossed constellation transformation algorithm for either square-framed or non-square-framed M-levelquadrature amplitude modulation(QAM) Nyquist systems is proposed.It is verified in 32-and 128-QAM systems that it can provide high linewidth tolerance with little complexity.     

Compensation for the self-steepening effects in optical fiber communication system using midway optical phase conjugation

Effects of self-steepening (SS) of chirped Gaussian pulses on optical fiber communication system using midway optical phase conjugation (OPC) are analyzed. Dynamic evolution of the ultrashort pulses is simulated numerically. It is found that OPC cannot compensate for pulse waveform distortion due to SS.The initial chirp of pulses and dispersion can counteract SS and improve the compensation performance for the distortion.